22mm, Mexican War General Staff Officer coat button. "J. M. L. & W.  H. Scovill/Waterbury/ Extra Superfine" backmark.  This button's manufacture dates to the 1830's and it shows a lot of character.  It would be appropriate to display in a Seminole Indian War, Mexican War, or a Civil War collection (as they are still infrequently found on Civil War sites).